This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-294852, filed Sep. 27, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to, in particular, a silver halide photographic lightsensitive material whose deterioration of photographic properties due to radiation is alleviated.
2. Description of the Related Art
Recently, requirements of photographic lightsensitive materials, in particular, of image-taking photosensitive material have become stricter and stricter. In addition to high sensitivity, it is required to further reduce the graininess deterioration due to radiation exposure, and an improved emulsion to be used for the photographic material is required.
There is a technique of including tabular silver halide grains (hereinafter referred to as xe2x80x9ctabular grainsxe2x80x9d) in order to achieve a highly sensitive silver halide emulsion. A method of manufacturing and a technique of using tabular grains are disclosed in U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306, and 4,459,353, and Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as xe2x80x9cJP-A-xe2x80x9d) 59-99433 and JP-A-62-209445. Known advantages of tabular grains are an enhancement of sensitivity, including improvements in the color sensitizing efficiency by sensitizing dyes, improvements in the sensitivity/graininess relationship, improvements in the sharpness due to specific optical characteristics of tabular grains, and improvements in the covering power, etc. Generally, in order to improve the sensitivity of a silver halide emulsion, it is effective to use tabular grains of a large size and a high aspect ratio.
In the meantime, it has been gradually found that deterioration of photographic properties due to long-term storage of photographs is increased as sensitivity is improved more and more. In particular, it is a great problem in a color negative photographic lightsensitive material of ISO 400 or more. Deterioration of photographic properties due to long-term storage is caused by natural radiation (environmental radioactivity and cosmic rays), in addition to heat and moisture that are conventionally well known. The photosensitive materials exposed to natural radiation give raise to increment in fog density and deterioration of graininess. As measures against such deteriorations in photographic properties due to natural radiation, a method of reducing the application amount of silver (JP-A""s-63-226650 and 63-226651), and a method of reducing the potassium content in a photographic lightsensitive material (JP-A-2-836), etc. are known. In addition, as a method of reducing fog from radiation, disclosed are a method of adding methylocyan dyes (JP-A-2-190851), a method of using a compound other than chloroauric acid as a gold sensitizer (JP-A""s-4-67032, 4-68337 and 4-75053), and a method of forming development initiating points on the same plane (JP-A-5-216246). However, these documents only refer to techniques for improving the sensitivity and reducing the fog due to radiation, and do not clearly refer to a method of improving granularity which deteriorates due to radiation.
It was considered that the cause of deterioration of graininess due to radiation was the generation of locally high-density portions after development, because a plurality of grains are exposed by one photon of radiation. However, recently a cause other than the above has been clarified. It is reported that a plurality of development initiating points per grain are formed by irradiation of radiation. In such a case, when development is performed, only areas having the grains having a plurality of development initiating points per grain are developed early, and high-density portions locally appear. The greater the grain size of silver halide is, the more this effect is likely to occur (P. Broadhead., Imaging. Sci. J. 46. 107 (1998)). However, the above information only clarifies a phenomenon caused by radiation, and does not disclose at all a method of reducing the effects of radiation on granularity. As other measures for reducing the effects of radiation on granularity, there are a method of performing sufficient development (GB 2313673A), and a method of applying a physical pressure to a photosensitive material after application (WO00/38011). However, these methods are complicated and have problems for practical use. Further, these patents do not describe improvement of a reduction in the effects of radiation on granularity, by using the emulsion of the present invention.
Generally, it has been considered that the distribution of development initiating points in the case of performing exposure by light conforms to a Poisson distribution. Supposing that the ratio of grains having development initiating points of number x is P(x), P(x) is expressed by the following formula using the mean value n of development initiating points per grain.
P(x)=(exe2x88x92nxc3x97nx)/x!
However, it was not clear whether P(x) actually conforms to the above formula, and what distribution P(x) has in the case of performing exposure by radiation.
The inventors of the present invention have examined representative photographic lightsensitive materials. Thereby they have revealed that, in the case of performing exposure by light, the distribution of development initiating points conforms to a Poisson distribution, or is more concentrated than a Poisson distribution. Further, they have also revealed that, in the case of performing exposure by radiation, the distribution of development initiating points does not conform to a Poisson distribution, and the distribution is more dispersed than a Poisson distribution. Specifically, it was revealed that when enough light to expose 50-55% (number ratio) of the grains to have at least one respective development initiating point is applied, the ratio of the number of silver halide grains having two or more development initiating points per grain to the silver halide grains having at least one development initiating point of all the photographic lightsensitive materials that the present inventors measured, was less than 35%. In the meantime, when enough radiation to expose 50-55% (number ratio) of the grains to have at least one respective development initiating point is irradiated, the ratio of the number of silver halide grains having two or more development initiating points per grain to the silver halide grains having at least one development initiating point of all the photographic lightsensitive materials that the present inventors measured was, 45% or more. As described above, in the case of performing exposure by radiation, the number of development initiating points per grain is greater than that in the case of performing exposure by light, which causes the problem of deterioration of graininess.
An object of the present invention is to provide a photographic lightsensitive material whose granularity deterioration due to radiation is alleviated, and whose sensitivity/radiation fog ratio is improved.
As a result of diligent research, the inventor of the present invention has found that, an emulsion containing a smaller number of grains having a plurality of development initiating points per grain when irradiated, can be obtained by, for example, introducing a dislocation line inside the grains, adding a metal ion or metal complex inside the grains, or applying pressure inside the grains with a dissolver, into tabular grains each having a large grain size and a large aspect ratio. And the use of such an emulsion in a photosensitive material can alleviate granularity deterioration due to radiation and decrease sensitivity to radiation.
The above object has been achieved by the following items (1)-(7).
(1) A silver halide photographic lightsensitive material having at least one lightsensitive silver halide emulsion layer on a support, wherein at least one layer of the lightsensitive silver halide emulsion layers comprises a lightsensitive silver halide emulsion containing silver halide grains in which a ratio of xe2x80x9cthe number of silver halide grains having at least two development initiating points per grainxe2x80x9d to xe2x80x9cthe number of silver halide grains having at least one development initiating point per grainxe2x80x9d is 45% or less when the silver halide photographic lightsensitive material is subjected to radiation and subsequent development under the following conditions,
Conditions of irradiation:
(radiation source) gamma rays irradiated from 60Co (radiation amount) enough to expose 50-55% (number ratio) of the silver halide grains contained in the lightsensitive silver halide emulsion layer to have at least one development initiating point
Conditions of Development:
(Stop Solution)
3% acetic acid aqueous solution
(2) The silver halide photographic lightsensitive material of above item (1), wherein the ratio of xe2x80x9cthe number of silver halide grains having at least two development initiating points per grainxe2x80x9d to xe2x80x9cthe number of silver halide grains having at least one development initiating point per grainxe2x80x9d is 35% or less.
(3) The silver halide photographic lightsensitive material of above item (1) or (2), wherein the lightsensitive silver halide emulsion comprises silver iodobromide or silver iodochlorobromide tabular grains having (111) faces as main planes, an average equivalent sphere diameter of 0.8 xcexcm or more, and an average aspect ratio of 2 or more.
(4) The silver halide photographic lightsensitive material of above item (3), wherein the average aspect ratio of the tabular grains is 8 or more.
(5) The silver halide photographic lightsensitive material of above item (3), wherein the average aspect ratio of the tabular grains is 13 or more.
(6) The silver halide photographic lightsensitive material of above item (3), wherein the average aspect ratio of the tabular grains is 20 or more.
(7) The silver halide photographic lightsensitive material of any one of above items (3) to (6), wherein the average equivalent sphere diameter of the tabular grains is 1.0 xcexcm or more.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The silver halide photosensitive material of the present invention will now be described. One of the embodiments of a preferred photosensitive material is a silver halide photographic lightsensitive material containing at least one lightsensitive silver halide emulsion layer containing a silver halide emulsion wherein a ratio of the number of silver halide grains having two or more development initiating points per grain to silver halide grains having one or more development initiating point per grain is 45% or less, when performing irradiation and performing development thereafter under the following conditions. If the ratio of the number of silver halide grains having two or more development initiating points per grain to silver halide grains having one or more development initiating points per grain exceeds 45%, graininess is not improved, which is not desirable. The ratio of the number of silver halide grains having two or more development initiating points per grain to silver halide grains having one or more development initiating points per grain is, more preferably, 35% or less.
Although the term xe2x80x9cradiationxe2x80x9d in the present invention mainly means natural radiation, it may also mean artificial radiation. As a method of intentionally irradiating radiation, gamma rays of 60Co can be used, for example. The radiation conditions in the present invention means an amount needed to initiate development initiating points of 50-55% (number ratio) of the emulsion grains in the lightsensitive silver halide emulsion layer, so as to have at least one respective development initiating points when gamma rays of 60Co of 37 GBq are irradiated to the emulsion for a certain time at a distance of 1 m from its source.
The development initiating point in the present invention means a point recognized as a point where development starts, by viewing the layer after performing the following development processing and stop processing.
Development Conditions:
(Stop Solution)
3% acetic acid aqueous solution
The number and locations of development initiating points formed on surfaces of grains can be searched as follows.
Specifically, a silver halide color photographic lightsensitive material is irradiated by an exposure corresponding to its effective imaging region, which is an exposure amount that is enough for 50-55% (number ratio) of the grains contained in an emulsion to have at least one development initiating point, and thereafter the developed silver formed by the development is observed through a microscope to obtain the number and locations of development initiating points.
Specifically, an irradiated silver halide photosensitive material is developed, and thereafter is soaked in an acetic acid solution to stop development and washed. Thereafter, the emulsion surface is soaked in a gelatin-degradating enzyme solution, and thereby films are stripped successively from an upper emulsion layer until reaching an emulsion layer to be observed. Then, carbon is deposited on the silver halide grains of the emulsion layer to be observed remaining on a support, and its reflecting electrons are observed by a scanning electron microscope (about 5,000-30,000 magnification).
The development initiating points are observed in a granular or filamentary form with a whitish color similar to silver halide grains, on a monochrome photograph taken by using a scanning electron microscope as described above.
Further, silver halide grains in a desired emulsion layer can be viewed even in a color photosensitive material of a multi-layer structure, by selecting the proper concentration of the gelatin-degradating enzyme solution and the proper time of soaking the material in the solution.
In the present invention, in order to research the number and locations of development initiating points formed on surfaces of tabular grains, it is desirable to observe development initiating points of at least 200 grains. For more precise research, 400 or more grains should be observed.
The form of silver halide emulsion used in a photosensitive material of the present invention (hereinafter referred to as xe2x80x9cemulsion of the present inventionxe2x80x9d) will now be described.
In the emulsion of the present invention, 50% or more of the total projected area is preferably occupied by silver iodobromide or silver iodochlorobromide tabular grains each having (111) faces as main planes. The term xe2x80x9ctabular silver halide grainxe2x80x9d is a generic term for a silver halide grain having a twin face or two or more parallel twin faces. The term xe2x80x9ctwin facexe2x80x9d means a (111) face in the case where ions of all lattice points on one side of the (111) face have a mirror-image relationship to respective corresponding lattice points on the other side of the (111) face. The tabular grain has a triangular, hexagonal, or circular shape of a rounded triangle or hexagon when the grain is viewed from the vertical direction with respect to its main planes. A triangular grain has triangular, a hexagonal grain has hexagonal, and a circular grain has circular main planes parallel to each other.
The distance between the twin planes of the tabular grain of the invention can be 0.012 xcexcm or less, as disclosed in U.S. Pat. No. 5,219,720. Also, the ratio of the distance between (111) main planes/the distance between twin planes can be 15 or more, as disclosed in JP-A-5-249585. The distances can be selected depending on purposes.
In the emulsion of the present invention, it is preferred that hexagonal tabular grains whose neighboring side ratio (maximum side length/minimum side length) is in the range of 1.5 to 1 occupy 100 to 50% of the total number of all the grains of the emulsion. The above hexagonal tabular grains more preferably occupy 100 to 70%, most preferably 100 to 80%, of the total number. In the emulsion of the present invention, it is especially preferred that hexagonal tabular grains whose neighboring side ratio (maximum side length/minimum side length) is in the range of 1.2 to 1 occupy 100 to 50% of the total number of all the grains of the emulsion. The above hexagonal tabular grains more preferably occupy 100 to 70%, most preferably 100 to 80%, of the total number. The mixing of tabular grains other than these hexagonal tabular grains into the emulsion is not favorable from the viewpoint of intergranular homogeneity.
The emulsion of the present invention contains tabular grains having an average equivalent sphere diameter of 0.8 xcexcm or more and an average aspect ratio of 2 or more. The average aspect ratio is preferably 8 or more, more preferably 13 or more, especially preferably 20 or more. The upper limit of the average aspect ration is preferably 200. Further, in any case, the average equivalent sphere diameter is especially preferably 1.0 xcexcm or more. The upper limit of the average equivalent sphere diameter is preferably 3.0 xcexcm.
In the case of using grains of values outside these ranges, it is difficult to obtain the advantages of the present invention, which is not preferable.
The term xe2x80x9cequivalent sphere diameterxe2x80x9d in the present invention means the diameter of a sphere having a volume equal to that of the grain.
Further, the term xe2x80x9caspect ratioxe2x80x9d in the present invention means the ratio of an equivalent circle diameter to the thickness of a silver halide grain. The term xe2x80x9cequivalent circle diameterxe2x80x9d means the diameter of a circle having an area equal to the projected area of a parallel outer surface of the grain. Specifically, an aspect ratio is the value obtained by dividing a circle equivalent diameter of a projected area of an individual silver halide grain by the thickness of the grain. As an example of a method of measuring the aspect ratio, there is a method of determining a diameter (equivalent circle diameter) and thickness of a circle having an area equal to the projected area of an individual grain by taking a transmission electron microscope photograph by means of replica plating. In this case, the thickness is calculated from the length of the shadow of a replica.
The average grain thickness of tabular grains of the present invention is preferably 0.03-0.60 xcexcm, more preferably 0.05-0.30 xcexcm, further preferably 0.05-0.20 4 xcexcm, especially preferably 0.05-0.15 xcexcm. The term xe2x80x9caverage grain thicknessxe2x80x9d means an arithmetic mean of the grain thickness of all tabular grains in the emulsion. An emulsion having an average grain thickness less than 0.03 xcexcm is difficult to prepare. If the average grain thickness of an emulsion exceeds 0.60 xcexcm, it is hard to obtain the merits of the tabular grains, which is not preferable.
The average equivalent circle diameter of tabular grains of the present invention is preferably 0.8-6.0 xcexcm, more preferably 1.0-5.5 xcexcm, further preferably 1.5-5.5 xcexcm. The term xe2x80x9caverage equivalent circle diameterxe2x80x9d means an arithmetic mean of equivalent circle diameters of all the tabular grains in the emulsion. If the average diameter does not fall within these ranges, it is hard to obtain the advantage of the present invention, which is not preferable.
It is preferred that the emulsion of the present invention be composed of monodisperse grains. In the present invention, the variation coefficient of grain size (equivalent sphere diameter) distribution of all silver halide grains is preferably in the range of 35 to 3%, more preferably 20 to 3%, and most preferably 15 to 3%. The terminology xe2x80x9cvariation coefficient of equivalent sphere diameter distributionxe2x80x9d used herein means the product obtained by dividing the dispersion (standard deviation) of equivalent sphere diameters of individual tabular grains by the average equivalent sphere diameter and multiplying the resultant quotient by 100. That the variation coefficient of equivalent sphere diameter distribution of all tabular grains exceeds 35% is not favorable from the viewpoint of intergranular homogeneity. On the other hand, it is difficult to prepare an emulsion wherein the variation coefficient is below 3%.
The variation coefficient of equivalent circle diameter distribution of all grains contained in the emulsion of the present invention is preferably in the range of 40 to 3%, more preferably 25 to 3%, and most preferably 15 to 3%. The terminology xe2x80x9cvariation coefficient of equivalent circle diameter distributionxe2x80x9d used herein means the product obtained by dividing the dispersion (standard deviation) of equivalent circle diameters of individual grains by the average equivalent circle diameter and multiplying the resultant quotient by 100. That the variation coefficient of equivalent circle diameter distribution of all grains exceeds 40% is not favorable from the viewpoint of intergranular homogeneity. On the other hand, it is difficult to prepare an emulsion wherein the variation coefficient i s below 3%.
The variation coefficient of grain thickness distribution of all tabular grains contained in the emulsion of the present invention is preferably in the range of 25 to 3%, more preferably 20 to 3%, and most to preferably 15 to 3%. The terminology xe2x80x9cvariation coefficient of grain thickness distributionxe2x80x9d used herein means the product obtained by dividing the dispersion (standard deviation) of grain thicknesses of individual tabular grains by the average grain thickness and multiplying the resultant quotient by 100. That the variation coefficient of grain thickness distribution of all tabular grains exceeds 25% is not favorable from the viewpoint of intergranular homogeneity. On the other hand, it is difficult to prepare an emulsion wherein the variation coefficient is below 3%.
The variation coefficient of distribution of distance between twin planes of all tabular grains contained in the emulsion of the present invention is preferably in the range of 25 to 3%, more preferably 20 to 3%, and most preferably 15 to 3%. The terminology xe2x80x9cvariation coefficient of distribution of distance between twin planesxe2x80x9d used herein means the product obtained by dividing the dispersion (standard deviation) of distance between twin planes of individual tabular grains by the average distance between twin planes and multiplying the resultant quotient by 100. That the variation coefficient of distance between twin planes of all tabular grains exceeds 25% is not favorable from the viewpoint of intergranular homogeneity. On the other hand, it is difficult to prepare an emulsion wherein the variation coefficient is below 3%.
In the present invention, although the grain thickness, aspect ratio and monodispersity can be selected within the above ranges in conformity with the purpose of the use thereof, it is desirable to employ monodisperse tabular grains of small grain thickness and high aspect ratio.
In the present invention, various methods can be employed for the formation of tabular grains of high aspect ratio. For example, the grain forming methods described in U.S. Pat. Nos. 5,496,694 and 5,498,516, can be employed.
In the production of monodisperse tabular grains of high aspect ratio, it is important to form twinned crystal nuclei of small size within a short period of time. Thus, it is desirable to perform nucleation within a short period of time under low temperature, high pBr, low pH and small gelatin amount conditions. With respect to the type of gelatin, a gelatin of low molecular weight, a gelatin whose methionine content is low or a gelatin whose amino group is modified with, for example, phthalic acid, trimellitic acid or pyromellitic acid and the like are preferably employed.
After the nucleation, physical ripening is performed to thereby eliminate nuclei of regular crystals, single twinned crystals and nonparallel multiple twinned crystals while selectively causing nuclei of parallel double twinned crystals to remain. Further ripening among the remaining nuclei of parallel double twinned crystals is preferable from the viewpoint of enhancing the monodispersity.
Also, it is preferable to perform the physical ripening, for example, in the presence of PAO (polyalkylene oxide) as described in U.S. Pat. No. 5,147,771, from the viewpoint of enhancing the monodispersity.
Thereafter, supplemental gelatin is added, and soluble silver salts and soluble halides are added to thereby effect a grain growth. The above gelatin whose amino group is modified with, for example, phthalic acid, trimellitic acid or pyromellitic acid is preferably employed as the supplemental gelatin.
Further, the grain growth can preferably be performed by adding silver halide fine grains separately prepared in advance or simultaneously prepared in a separate reaction vessel to thereby feed silver and halide.
During the grain growth as well, it is important to control and optimize the temperature of reaction mixture, pH, amount of binder, pBr, feeding speeds of silver and halide ion, etc.
In the formation of silver halide emulsion grains for use in the present invention, it is preferable to employ silver iodobromide or silver chloroiodobromide. When there is a phase containing an iodide or a chloride, the phase may be uniformly distributed in each grain, or may be localized therein.
Furthermore, other silver salts, such as silver rhodanate, silver sulfide, silver selenide, silver carbonate, silver phosphate and an organic acid salt of silver, may be contained in the form of other separate grains or as parts of silver halide grains.
In the emulsion grains of the present invention, the silver bromide content is preferably 80 mol % or more, more preferably 90 mol % or more.
The silver iodide content of the emulsion of the present invention is preferably in the range of 1 to 20 mol %, more preferably 2 to 15 mol %, and most preferably 3 to 10 mol %. Silver iodide contents of less than 1 mol % are not suitable because it becomes difficult to realize the effects of enhancing dye adsorption, increasing of intrinsic photographic speed, etc. On the other hand, silver iodide contents of more than 20 mol % are not suitable because the development velocity is generally delayed.
The variation coefficient of intergranular silver iodide content distribution in the emulsion grains for use in the present invention is preferably 30% or less, more preferably 25 to 3%, and most preferably 20 to 3%. That the variation coefficient exceeds 30% is not favorable from the viewpoint of intergranular homogeneity. The terminology xe2x80x9cvariation coefficient of intergranular silver iodide content distributionxe2x80x9d used herein means the product obtained by dividing the standard deviation of silver iodide contents of individual emulsion grains by the average silver iodide content and multiplying the resultant quotient by 100. The silver iodide contents of individual emulsion grains can be measured by analyzing the composition of each individual grain by means of an X-ray microanalyzer.
The measuring method is described in, for example, EP No. 147,868. In the determination of the distribution of silver iodide contents of individual grains contained in the emulsion of the present invention, the silver iodide contents are preferably measured with respect to at least 100 grains, more preferably at least 200 grains, and most preferably at least 300 grains.
Each of the emulsion grains of the invention mainly comprises (111) faces and (100) faces. A ratio of an area occupied by (111) faces to all the surface area of the emulsion grains is preferably at least 70%.
On the other hand, the portion where (100) faces appear in the emulsion grains of the invention is at side surfaces of the tabular grains. The ratio of an area occupied by (100) faces to the surface area of the emulsion grains, to an area occupied by (111) faces to the surface area of the emulsion grains is preferably at least 2%, more preferably 4% or more. The control of the (100) face ratio can be conducted by referring to the descriptions in JP-A""s-2-298935 and 8-334850. The ratio of (100) face can be measured by a method that uses difference of adsorption dependency between (111) face and (100) face to a spectral sensitizing dye, for example, the method described in Tani, J. Imaging Sci., 29, 165(1985).
In the emulsion grains used in the invention, an area ratio of (100) faces in the side faces of the tabular grains is preferably 15% or more, and more preferably 25% or more. The area ratio of (100) faces in the side faces of the tabular grains can be obtained by the method described, for example, in JP-A-8-334850.
That is, letting Cub be the ratio of the area which (111) faces occupy on the surface of an emulsion grain to the area which (100) faces occupy on the grain surface, an area ratio ECub of (100) faces in side faces of a tabular grain is
xe2x80x83Cubxc3x97(ECD+2t)/2t
where
ECD: average equivalent-circle diameter (xcexcm)
t: average grain thickness (xcexcm)
More specifically, the (100) face ratio is controlled by controlling the pAg, halogen composition, silver halide solvent concentration, and pH during the formation of silver halide grains, or by using a compound represented by formula (I) below.
YO(CH2CH2O)m(CH(CH3)CH2O)p(CH2CH2O)nYxe2x80x83xe2x80x83(I)
In formula (I), Y represents a hydrogen atom, xe2x80x94SO3M, or xe2x80x94COBCOOM, M represents a hydrogen atom, an alkali metal atom, an ammonium group, or an alkyl-substituted ammonium group having 5 or less A carbon atoms, B represents a chainlike or cyclic group for forming an organic dibasic acid, each of m and n represents an integer of 0 to 50, and p represents an integer of 1 to 100. 
In the present invention, the addition amount of these compounds are preferably 5xc3x9710xe2x88x922 g to 10 g per mol of silver halide.
Next, there will be described a specific example of an emulsion containing silver halide grains in which the ratio of the number of silver halide grains having two or more development initiating points per grain to silver halide grains having one or more development initiating point per grain does not exceed 45% in the present invention. In the present invention, such an emulsion can be preferably prepared by (1) introducing dislocation lines inside grains, (2) adding metal ions or metal complexes inside grains, and/or (3) applying pressure to grains by a high-speed agitator using dissolver wings. However, the preparation methods are not limited to the above. The methods of above items (1)-(3) may be used individually, or two or more methods may be combined. Further, the present invention is not limited to these methods.
The tabular grains in the present invention preferably have dislocation lines inside the respective grains. A preferable grain has at least 10 dislocation lines per grain, more preferably at least 20 dislocation lines, further preferably at least 30 dislocation lines inside the grain. The introduction of dislocation lines into a tabular grain will now be described below.
A dislocation line is a linear lattice defect at the boundary between a region already slipped and a region not slipped yet on a slip plane of crystal. Dislocation lines in a silver halide crystal are described in, e.g., 1) C. R. Berry. J. Appl. Phys., 27, 636 (1956); 2) C. R. Berry, D. C. Skilman, J. Appl. Phys., 35, 2165 (1964); 3) J. F. Hamilton, Phot. Sci. Eng., 11, 57 (1967); 4) T. Shiozawa, J. Soc. Photo. Sci. Jap., 34, 16 (1971); and 5) T. Shiozawa, J. Soc. Phot. Sci. Jap., 35, 213 (1972). Dislocation lines can be analyzed by an X-ray diffraction method or a direct observation method using a low-temperature transmission electron microscope. In direct observation of dislocation lines using a transmission electron microscope, silver halide grains, extracted carefully from an emulsion so as not to apply a pressure by which dislocation lines are produced in the grains, are placed on a mesh for electron microscopic observation. While the sample is cooled in order to prevent damage (e.g., print out) due to electron rays, the observation is performed by a transmission method.
In this case, as the thickness of a grain increases, it becomes more difficult to transmit electron rays through it. Therefore, grains can be observed more clearly by using an electron microscope of high voltage type (200 kV or more for a thickness of 0.25 xcexcm).
In the present invention, dislocation lines are preferably introduced into a tabular grain as follows. That is, dislocation lines are introduced by the epitaxial growth of a silver halide phase containing silver iodide to a tabular grain (also called a host grain) as a substrate and the formation of a silver halide shell after that.
The silver iodide content of the host grain is preferably 0 to 15 mol %, more preferably, 0 to 12 mol %, and most preferably, 0 to 10 mol %. However, this silver iodide content can be selected in accordance with the intended use. A silver iodide content exceeding 15 mol % is unpreferable because the developing speed generally lowers.
The silver iodide content in the composition of the silver halide phase epitaxially grown on the host grain is preferably as high as possible. Although this silver halide phase to be epitaxially grown can be any of silver iodide, silver iodobromide, silver iodochlorobromide, and silver iodochloride, it is preferably silver iodide or silver iodobromide, and more preferably, silver iodide. When the silver halide phase is silver iodobromide, the silver iodide (iodide ion) content is preferably 1 to 45 mol %, more preferably, 5 to 45 mol %, and most preferably, 10 to 45 mol %. This silver iodide content is preferably as high as possible to form a misfit necessary to introduce dislocation lines. However, 45 mol % is the solid solution limit of silver iodobromide.
The amount of halogen added to form this high-silver-iodide-content phase to be epitaxially grown on the host grain is preferably 2 to 15 mol %, more preferably, 2 to 10 mol %, and most preferably, 2 to 5 mol % of the silver amount of the host grain. If the halogen amount is less than 2 mol %, dislocation lines are difficult to introduce. If the halogen amount exceeds 15 mol %, the developing speed lowers.
This high-silver-iodide-content phase is preferably 5 to 30 mol %, more preferably, 5 to 20 mol % of the silver amount of the whole grain when viewed from outside the grain. An amount less than 5 mol % or exceeding 30 mol % is unpreferable because it is difficult to increase the sensitivity by the introduction of dislocation lines.
Also, this high-silver-iodide-content phase can be formed in any portion on the host grain, i.e., it can cover the host grain or can be formed only in a particular portion. It is preferable to control the positions of dislocation lines in a grain by selecting a particular portion and epitaxially growing the phase.
In the present invention, the high-silver-iodide-content phase is most preferably formed on side faces and/or corners of a host tabular grain. In this formation, it is possible to freely choose the composition and addition method of a halide to be added and the temperature, pAg, solvent concentration, gelatin concentration, and ionic strength of a reaction solution. The high-silver-iodide-content phase in a grain can be measured by an analytical electron microscope described in, e.g., JP-A-7-219102.
When this high-silver-iodide-content phase is formed on the host grain in the present invention, it is possible to preferably use, e.g., a method of adding a water-soluble iodide solution, such ad potassium iodide, singly or together with a water-soluble silver salt solution such as silver nitrate, a method of adding a silver halide containing silver iodide in the form of fine grains, or a method described in U.S. Pat. No. 5,498,516 or U.S. Pat. No. 5,527,664, the disclosers of which are incorporated herein by reference, by which iodide ions are released from an iodide ion-releasing agent by the reaction with alkali or a nucleophilic agent.
After this high-silver-iodide-content phase is epitaxially grown on the host grain, dislocation lines are introduced when a silver halide shell is formed outside the host tabular grain. Although the composition of this silver halide shell can be any of silver bromide, silver iodobromide, and silver iodochlorobromide, it is preferably silver bromide or silver iodobromide.
When the silver halide shell is silver iodobromide, the silver iodide content is preferably 0.1 to 12 mol %, more preferably, 0.1 to 10 mol %, and most preferably, 0.1 to 3 mol %.
If this silver iodide content is less than 0.1 mol %, it is difficult to obtain the advantages of enhancing dye adsorption and promoting development. If the silver iodide content exceeds 12 mol %, the developing speed generally lowers.
A silver amount used in the growth of this silver halide shell is preferably 5 to 30 mol %, and more preferably, 5 to 20 mol % of the total grain silver amount.
In the process of introducing dislocation lines described above, the temperature is preferably 30 to 80xc2x0 C., more preferably, 35 to 75xc2x0 C., and most preferably, 35 to 60xc2x0 C. Temperature control at low temperatures less than 30xc2x0 C. or at high temperatures exceeding 80xc2x0 C. requires a high performance manufacturing apparatus, and this is unfavorable for the manufacture. In the above dislocation line introducing process, the pAg is preferably 6.4 to 10.5.
In the case of tabular grains, positions and the number of dislocation lines of each grain when it is viewed from the position perpendicular to its main plane can be determined by an electron microscope photograph of grains taken as described above. When dislocation lines are introduced into the tabular grains of the present invention, in order to lower the sensitivity to radiation, it is preferable to introduce dislocation lines as inward as possible. In the silver halide grains of the present invention, it is preferable that each of the grains occupying at least 50 mol %, preferably at least 80 mol %, more preferably 100 mol % of silver halide of all the grains has dislocation lines which are localized in a region from 10% to 80% of the grain volume (i.e. as the volume of the grain from the center to the periphery thereof) of the silver halide grain. It is more preferable that dislocation lines are localized inside a grain in an area corresponding to 30% to 70% of the grain volume. The sensitivity to radiation is not lowered if dislocation lines are introduced at a position exceeding 80% from the center of the grain volume. Further, it is not preferable to introduce dislocation lines at a position less than 10% from the center of the grain volume, since thin tabular silver halide grains do not grow.
However, it is preferable to introduce dislocation lines also in a fringe portion for the purpose of improving the sensitivity and pressure properties. As a method of introducing dislocation lines in a fringe portion, the methods disclosed in JP-A""s-63-220238, 1-201649 and 6-258745, for example, can be preferably used.
The tabular grains in the present invention preferably contain at least one kind of photographically useful metal ion or complex (hereinafter referred to as xe2x80x9cmetal (complex) ionsxe2x80x9d) inside the grains.
Metal ion doping into silver halide grains will now be described.
The useful metal (complex) ions in the present invention are doped into grains for the purpose of improving the sensitivity to radiation, and improving the graininess of a lightsensitive silver halide emulsion. These compounds work as transient or permanent traps for electrons or positive holes in silver halide crystals to lower the sensitivity to radiation and to concentrate development initiating points, thereby to produce advantages such as in alleviation of graininess deterioration caused by radiation.
As the metal for use in doping within emulsion grains in the present invention, there can preferably be employed the first to third transition metal elements such as iron, ruthenium, rhodium, palladium, cadmium, rhenium, osmium, iridium, platinum, chromium and vanadium and further amphoteric metal elements such as gallium, indium, thallium and lead. These metal ions are doped in the form of a complex salt or a single salt. With respect to the complex ion, a six-coordinate halogeno or cyano complex containing halide ion or cyanide (CN) ion as a ligand is preferably used.
Also, use can be made of a complex having a nitrosyl (NO) ligand, a thionitrosyl (NS) ligand, a carbonyl (CO) ligand, a thiocarbonyl (NCO) ligand, a thiocyanato (NCS) ligand, a selenocyanato (NCSe) ligand, a tellurocyanato (CNTe) ligand, a dinitrogen (N2) ligand, an azido (N3) ligand or an organic ligand such as a bipyridyl ligand, a cyclopentadienyl ligand, a 1,2-dithiolenyl ligand or an imidazolyl ligand. The following polydentate ligands may be used as the ligand. That is, use may be made of any of bidentate ligands such as a bipyridyl ligand, tridentate ligands such as diethylenetriamine, tetradentate ligands such as triethylenetetramine and hexadentate ligands such as ethylenediaminetetraacetic acid. The coordination number is preferably 6, but may be 4. With respect to the organic ligand, those described in U.S. Pat. Nos. 5,457,021, 5,360,712 and 5,462,849, the disclosures of which are incorporated herein by reference, can preferably be employed. Further, it is also preferred to incorporate the metal ion in the form of an oligomer as described in U.S. Pat. No. 5,024,939.
When the metal (complex) ion is incorporated in a silver halide, it is important whether the size of metal (complex) ion is suitable to the lattice spacing of silver halide. Further, that a compound with the silver or halide ion of the metal (complex) ion is co-precipitated together with the silver halide is essential for the doping of the silver halide with the metal (complex) ion. Accordingly, it is required that the pKsp (common logarithm of inverse number of solubility product) of the compound with the silver or halide ion of the metal (complex) ion be approximately equal to the pKsp (silver chloride 9.8, silver bromide 12.3, and silver iodide 16.1) of silver halide. Therefore, the pKsp of the compound with the silver or halide ion of the metal (complex) ion is preferably in the range of 8 to 20.
The amount of metal complex with which silver halide grains are doped is generally in the range of 10xe2x88x929 to 10xe2x88x922 mol per mol of silver halide. Specifically, the amount of metal complex which provides a transient shallow electron trap in the photo-stage is preferably in the range of 10xe2x88x927 to 10xe2x88x922 mol. On the other hand, the metal complex which provides a deep electron trap in the photo-stage is preferably used in an amount of 10xe2x88x929 to 10xe2x88x925 mol, per mol of silver halide. For example, the doping amount of RhCL63xe2x88x92, which is used for deep trapping, is preferable 10xe2x88x929 to 10xe2x88x925 mol per mol of silver, more preferably 10xe2x88x928 to 10xe2x88x926 mol. The doping amount of IrCl64xe2x88x92, which is used for shallower trapping than RhCl63xe2x88x92, is preferable 10xe2x88x929 to 10xe2x88x924 mol per mol of silver, and more preferably 10xe2x88x928 to 10xe2x88x925 mol.
The content of metal (complex) ion in emulsion grains can be determined by the atomic absorption, polarized Zeeman spectroscopy and ICP analysis. The ligand of metal complex ion can be identified by the infrared absorption (especially, FT-IR).
When doping the above metal (complex) ions into the tabular grains of the present invention, it is preferable to dope the ions into the grains as centrally internal as possible in order to lower the sensitivity to radiation. In the silver halide grains of the present invention, it is preferable that each of grains occupying at least 50 mol %, preferably at least 80 mol %, more preferably 100 mol % of silver halide of all the grains has metal (complex) ions which are localized in 10% to 80% of the grain volume (i.e. anywhere from the center to the periphery of the grain) of the silver halide grain. It is more preferable that metal (complex) ions are localized inside a grain in an area corresponding to 30% to 70% of the grain volume. The sensitivity to radiation is not lowered if metal (complex) ions are introduced at a position exceeding 80% from the center of the grain volume. Further, it is not preferable to introduce metal (complex) ions at a position not exceeding 10% from the center of the grain volume, since thin tabular silver halide grains do not grow.
Further, when doping the above metal (complex) ions into the tabular grains of the present invention, a plurality of metal ions may be doped. The ions may be doped in the same phase, or doped in different phases. As a method of adding these compounds, the metallic salt solution may be added by mixing it into a halide aqueous solution or a water-soluble silver salt solution when forming the grains, or the metallic salt solution may be directly added. Further, silver halide emulsion fine grains doped with the metal ions may be added. When dissolving metallic salt in an appropriate solvent such as water, methanol or acetone, it is preferable to add a hydrogen halide aqueous solution (for example, HCl, HBr), thiocyanic acid or a salt thereof, or alkali halide (for example, KCl, NaCl, KBr, NaBr). Furthermore, it is preferable at the same point to add an acid or alkali and the like according to necessity.
In the case of doping metal ions of a cyano complex into emulsion grains, sometimes cyanogen is generated by the reaction between gelatin and the cyano complex and gold sensitization is inhibited. In such cases, it is preferable to also use a compound which inhibits the reaction between the gelatin and cyano complex, as described in JP-A-6-308653, for example. Specifically, it is preferable to perform the step of doping metal ions of cyano complex and the subsequent steps, under the presence of metal ions such as zinc ions, to coordinate with the gelatin.
Pressure is preferably applied to grains of the silver halide of the present invention by a high-speed agitator using dissolver wings, for example. When pressure is applied to grains, defects are generated inside the grains, and the defects serve as internal traps to reduce the sensitivity of the grains to radiation. With respect to a high-speed agitator using dissolver wings, a device described in JP-A-58-105141 is preferably used.
When pressure is applied to the silver halide of the present invention by a high-speed agitator using dissolver wings, it is preferable to increase the rpm as high as possible unless the silver halide is fogged by pressure. For example, it is preferable to agitate the silver halide at 5000-10000 rpm for 30-180 minutes. A sufficient pressure cannot be obtained with 5000 rpm or less, which does not lower the sensitivity to radiation and is not preferable. Further, an rpm exceeding 10000 rpm is not preferable, since too much pressure is applied to the silver halide, causing fog of the silver halide.
The period during which a pressure is applied to the silver halide of the present invention by a dissolver must precede the application of an emulsion. Further, the period for applying pressure preferably follows grain formation, more preferably follows spectral sensitization and/or chemical sensitization.
Emulsions of the present invention and other photographic emulsions that can be used together with the emulsions of the present invention can be prepared by the methods described in, e.g., P. Glafkides, Chimie et Physique Photographique, Paul Montel, 1967; G. F. Duffin, Photographic Emulsion Chemistry, Focal Press, 1966; and V. L. Zelikman et al., Making and Coating Photographic Emulsion, Focal Press, 1964. That is, any of an acid method, a neutral method, and an ammonia method can be used. In forming grains by the reaction of a soluble silver salt and a soluble halogen salt, any of the single-jet method, the double-jet method, and the combination of these methods can be used. It is also possible to use a method (so-called reverse double-jet method) of forming grains in the presence of excess silver ion. As one type of the double-jet method, a method in which the pAg of a liquid phase for producing a silver halide is maintained constant, i.e., a so-called controlled double-jet method can be used. This method makes it possible to obtain a silver halide emulsion in which the crystal shape is regular and the grain size is nearly uniform.
In some cases, it is preferable to make use of a method of adding silver halide grains already formed by precipitation to a reactor vessel for emulsion preparation, and the methods described in U.S. Pat. Nos. 4,334,012, 4,301,241, and 4,150,994, the discloses of which are herein incorporated by reference. These silver halide grains can be used as seed crystal and are also effective when supplied as a silver halide for growth. In the latter case, addition of an emulsion with a small grain size is preferable. The total amount of an emulsion can be added at one time, or an emulsion can be separately added a plurality of times or added continuously. In addition, it is sometimes effective to add grains having several different halogen compositions in order to modify the surface.
A method of converting most of or only a part of the halogen composition of a silver halide grain by a halogen conversion process is disclosed in, e.g., U.S. Pat. Nos. 3,477,852 and 4,142,900, European Patents (hereinafter also referred to as EU) 273,429 and 273,430, and West German Patent 3,819,241, the disclosers of which are incorporated herein by reference. This method is an effective grain formation method. To convert into a silver salt that is more sparingly soluble, it is possible to add a solution of a soluble halogen or silver halide grains. The conversion can be performed at one time, separately a plurality of times, or continuously.
As a grain growth method other than the method of adding a soluble silver salt and a halogen salt at a constant concentration and a constant flow rate, it is preferable to use a grain formation method in which the concentration or the flow rate is changed, such as described in British Patent (hereinafter also referred to as GB) 1,469,480 and U.S. Pat. Nos. 3,650,757 and 4,242,445, the disclosures of which are incorporated herein by reference. Increasing the concentration or the flow rate can change the amount of a silver halide to be supplied as a linear function, a quadratic function, or a more complex function of the addition time. It is also preferable to decrease the silver halide amount to be supplied if necessary depending on the situation. Furthermore, when a plurality of soluble silver salts of different solution compositions are to be added, a plurality of soluble halogen salts of different solution compositions are to be added or a method of increasing one of the salts while decreasing the other is also effective.
A mixing vessel for reacting solutions of soluble silver salts and soluble halogen salts can be selected from those described in U.S. Pat. Nos. 2,996,287, 3,342,605, 3,415,650, and 3,785,777 and West German Patents 2,556,885 and 2,555,364, the disclosures of which are incorporated herein by reference.
A silver halide solvent is useful for the purpose of accelerating ripening. As an example, it is known to make an excess of halogen ion exist in a reactor vessel in order to accelerate ripening. Another ripening agent can also be used. The total amount of these ripening agents can be mixed in a dispersing medium placed in a reactor vessel before addition of a silver salt and a halide salt or can be introduced to the reactor vessel simultaneously with addition of a halide salt, a silver salt, and a deflocculant. Alternatively, ripening agents can be independently added in the step of adding a halide salt and a silver salt.
Examples of the ripening agent are ammonia, thiocyanate (e.g., potassium rhodanate and ammonium rhodanate), an organic thioether compound (e.g., compounds described in U.S. Pat. Nos. 3,574,628, 3,021,215, 3,057,724, 3,038,805, 4,276,374, 4,297,439, 3,704,130, and 4,782,013 and JP-A-57-104926), a thione compound (e.g., four-substituted thioureas described in JP-A-53-82408, JP-A-55-77737, and U.S. Pat. No. 4,221,863, and compounds described in JP-A-53-144319), mercapto compounds capable of accelerating growth of silver halide grains, described in JP-A-57-202531, and an amine compound (e.g., JP-A-54-100717).
It is advantageous to use gelatin as a protective colloid for use in the preparation of emulsions of the present invention or as a binder for other hydrophilic colloid layers. However, another hydrophilic colloid can also be used in place of gelatin.
Examples of the hydrophilic colloid are protein such as a gelatin derivative, a graft polymer of gelatin and another high polymer, albumin, and casein; cellulose derivatives such as hydroxyethylcellulose, carboxymethylcellulose, and cellulose sulfates; sugar derivatives such as soda alginate and a starch derivative; and a variety of synthetic hydrophilic high polymers such as homopolymers or copolymers, e.g., polyvinyl alcohol, polyvinyl alcohol partial acetal, poly-N-vinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylimidazole, and polyvinyl pyrazole.
Examples of gelatin are lime-processed gelatin, oxidated gelatin, and enzyme-processed gelatin described in Bull. Soc. Sci. Photo. Japan. No. 16, p. 30 (1966). In addition, a hydrolyzed product or an enzyme-degradating product of gelatin can also be used.
It is preferable to wash with water an emulsion of the present invention to desalt, and disperse into a newly prepared protective colloid. Although the temperature of washing can be selected in accordance with the intended use, it is preferably 5xc2x0 C. to 50xc2x0 C. Although the pH of washing can also be selected in accordance with the intended use, it is preferably 2 to 10, and more preferably, 3 to 8. The pAg of washing is preferably 5 to 10, though it can also be selected in accordance with the intended use. The washing method can be selected from noodle washing, dialysis using a semipermeable membrane, centrifugal separation, coagulation precipitation, and ion exchange. The coagulation precipitation can be selected from a method using sulfate, a method using an organic solvent, a method using a water-soluble polymer, and a method using a gelatin derivative.
It is sometimes useful to perform a method of adding a chalcogen compound during preparation of an emulsion, such as described in U.S. Pat. No. 3,772,031. In addition to S, Se, and Te, cyanate, thiocyanate, selenocyanic acid, carbonate, phosphate, and acetate can be present.
In the formation of silver halide grains of the present invention, at least one of chalcogen sensitization including sulfur sensitization and selenium sensitization, and noble metal sensitization including gold sensitization and palladium sensitization, and reduction sensitization can be performed at any point during the process of manufacturing a silver halide emulsion. The use of two or more different sensitizing methods is preferable. Several different types of emulsions can be prepared by changing the timing at which the chemical sensitization is performed. The emulsion types are classified into: a type in which a chemical sensitization nucleus is embedded inside a grain, a type in which it is embedded in a shallow position from the surface of a grain, and a type in which it is formed on the surface of a grain. In emulsions of the present invention, the position of a chemical sensitization speck can be selected in accordance with the intended use. However, it is preferable to form at least one type of a chemical sensitization nucleus in the vicinity of the surface.
One chemical sensitization which can be preferably performed in the present invention is chalcogen sensitization, noble metal sensitization, or a combination of these. The sensitization can be performed by using active gelatin as described in T. H. James, The Theory of the Photographic Process, 4th ed., Macmillan, 1977, pages 67 to 76. The sensitization can also be performed by using any of sulfur, selenium, tellurium, gold, platinum, palladium, and iridium, or by using a combination of a plurality of these sensitizers at pAg 5 to 10, pH 5 to 8, and a temperature of 30xc2x0 C. to 80xc2x0 C., as described in Research Disclosure, Vol. 120, April, 1974, 12008, Research Disclosure, Vol. 34, June, 1975, 13452, U.S. Pat. Nos. 2,642,361, 3,297,446, 3,772,031, 3,857,711, 3,901,714, 4,266,018, and 3,904,415, and British Patent 1,315,755. In the noble metal sensitization, salts of noble metals, such as gold, platinum, palladium, and iridium, can be used. In particular, gold sensitization, palladium sensitization, or a combination of the both is preferred.
In the gold sensitization, it is possible to use known compounds, such as chloroauric acid, potassium chloroaurate, potassium aurithiocyanate, gold sulfide, and gold selenide. A palladium compound means a divalent or tetravalent salt of palladium. A preferable palladium compound is represented by R2PdX6 or R2PdX4 wherein R represents a hydrogen atom, an alkali metal atom, or an ammonium group and X represents a halogen atom, e.g., a chlorine, bromine, or iodine atom.
More specifically, the palladium compound is preferably K2PdCl4, (NH4)2PdCl6, Na2PdCl4, (NH4)2PdCl4, Li2PdCl4, Na2PdCl6, or K2PdBr4. It is preferable that the gold compound and the palladium compound be used in combination with thiocyanate or selenocyanate.
Examples of a sulfur sensitizer are hypo, a thiourea-based compound, a rhodanine-based compound, and sulfur-containing compounds described in U.S. Pat. Nos. 3,857,711, 4,266,018, and 4,054,457. The chemical sensitization can also be performed in the presence of a so-called chemical sensitization aid. Examples of a useful chemical sensitization aid are compounds, such as azaindene, azapyridazine, and azapyrimidine, which are known as compounds capable of suppressing fog and increasing sensitivity in the process of chemical sensitization. Examples of the chemical sensitization aid and the modifier are described in U.S. Pat. Nos. 2,131,038, 3,411,914, and 3,554,757, JP-A-58-126526, and G. F. Duffin, Photographic Emulsion Chemistry, pages 138 to 143.
It is preferable to also perform gold sensitization for emulsions of the present invention. An amount of a gold sensitizer is preferably 1xc3x9710xe2x88x924 to 1xc3x9710xe2x88x927 mol, and more preferably, 1xc3x9710xe2x88x925 to 5xc3x9710xe2x88x927 mol per mol of a silver halide. A preferable amount of a palladium compound is 1xc3x9710xe2x88x923 to 5xc3x9710xe2x88x927 mol per mol of a silver halide. A preferable amount of a thiocyan compound or a selenocyan compound is 5xc3x9710xe2x88x922 to 1xc3x9710xe2x88x926 mol per mol of a silver halide.
An amount of a sulfur sensitizer with respect to silver halide grains of the present invention is preferably 1xc3x9710xe2x88x924 to 1xc3x9710xe2x88x927 mol, and more preferably, 1xc3x9710xe2x88x925 to 5xc3x9710xe2x88x927 mol per mol of a silver halide.
Selenium sensitization is a preferable sensitizing method for emulsions of the present invention. Known labile selenium compounds are used in the selenium sensitization. Practical examples of the selenium compound are colloidal metal selenium, selenoureas (e.g., N,N-dimethylselenourea and N,N-diethylselenourea), selenoketones, and selenoamides. In some cases, it is preferable to perform the selenium sensitization in combination with one or both of the sulfur sensitization and the noble metal sensitization.
It is preferable to perform reduction sensitization during grain formation, after grain formation but before chemical sensitization, or during chemical sensitization of the silver halide emulsion.
Reduction sensitization performed in the present invention can be selected from a method of adding reduction sensitizers to a silver halide emulsion, a method called silver ripening in which grains are grown or ripened in a low-pAg ambient at pAg 1 to 7, and a method called high-pH ripening in which grains are grown or ripened in a high-pH ambient at pH 8 to 11. It is also possible to combine two or more of these methods.
The method of adding reduction sensitizers is preferred in that the level of reduction sensitization can be finely adjusted.
Known examples of the reduction sensitizer are stannous chloride, ascorbic acid and its derivatives, amines and polyamines, hydrazine derivatives, formamidinesulfinic acid, a silane compound, and a borane compound. In reduction sensitization of the present invention, it is possible to selectively use these reduction sensitizers or to use two or more types of compounds together. Preferable compounds as the reduction sensitizer are stannous chloride, thiourea dioxide, dimethylamineborane, and ascorbic acid and its derivatives. Although the addition amount of reduction sensitizers must be so selected as to meet the emulsion manufacturing conditions, a proper amount is 10xe2x88x927 to 10xe2x88x922 mol per mol of a silver halide.
The reduction sensitizer is, for example, added during grain formation by dissolving thereof to water, or organic solvents such as alcohols, glycols, ketones, esters, and amides. The reduction sensitizer can previously added to a reaction vessel, but it is preferable to add the reduction sensitize at a proper timing during grain growth. It is also possible to previously add the reduction sensitizer to a solution of a water-soluble silver salt or of an alkaline halide, thereby to precipitate silver halide grains using the solutions. It is also preferable to add a solution of the reduction sensitizer at several times separately during the grain growth or add the solution for a consecutive long period.
It is preferable to use an oxidizer for silver during the process of manufacturing emulsions of the present invention. An oxidizer for silver means a compound having an effect of converting metal silver into silver ion. A particularly effective compound is the one that converts very fine silver grains, as a by-product in the process of formation of silver halide grains and chemical sensitization, into silver ion. The silver ion produced can form a silver salt hard to dissolve in water, such as a silver halide, silver sulfide, or silver selenide, or a silver salt easy to dissolve in water, such as silver nitrate.
An oxidizer for silver can be either an inorganic or organic substance. Examples of the inorganic oxidizer are ozone, hydrogen peroxide and its adduct (e.g., NaBO2.H2O2.3H2O, 2NaCO3.3H2O2, Na4P2O7.2H2O2, and 2Na2SO4.H2O2.2H2O), peroxy acid salt (e.g., K2S2O8, K2C2O6, and K2P2O8), a peroxy complex compound (e.g., K2[Ti(O2)C2O4].3H2O, 4K2SO4.Ti(O2)OH.SO4.2H2O, and Na3[VO(O2)(C2H4)2.6H2O], permanganate (e.g., KMnO4), an oxyacid salt such as chromate (e.g., K2Cr2O7), a halogen element such as iodine and bromine, perhalogenate (e.g., potassium periodate), a salt of a high-valence metal (e.g., potassium hexacyanoferrate(II)), and thiosulfonate.
Examples of the organic oxidizer are quinones such as p-quinone, an organic peroxide such as peracetic acid and perbenzoic acid, and a compound for releasing active halogen (e.g., N-bromosuccinimide, chloramine T, and chloramine B).
Preferable oxidizers of the present invention are ozone, hydrogen peroxide and its adduct, a halogen element, an inorganic oxidizer of thiosulfonate, and an organic oxidizer of quinones. The combined use of the aforementioned reduction sensitizer and the oxidizer to silver is a preferable embodiment. The method of adding the oxidizer can be selected from the method of using the oxidizer followed by performing reduction sensitization, the vice versa thereof, or the method of making both of the oxidizer and the reduction sensitizer present at the same time. These methods can be performed at a grain formation step or a chemical sensitization step.
Photographic emulsions used in the present invention can contain various compounds in order to prevent fog during the manufacturing process, storage, or photographic processing of a sensitized material, or to stabilize photographic properties. Usable compounds are those known as an antifoggant or a stabilizer, for example, thiazoles, such as benzothiazolium salt, nitroimidazoles, nitrobenzimidazoles, chlorobenzimidazoles, bromobenzimidazoles, mercaptothiazoles, mercaptobenzothiazoles, mercaptobenzimidazoles, mercaptothiadiazoles, aminotriazoles, benzotriazoles, nitrobenzotriazoles, and mercaptotetrazoles (particularly 1-phenyl-5-mercaptotetrazole); mercaptopyrimidines; mercaptotriazines; a thioketo compound such as oxadolinethione; azaindenes, such as triazaindenes, tetrazaindenes (particularly hydroxy-substituted(1,3,3a,7)tetrazaindenes), and pentazaindenes. For example, compounds described in U.S. Pat. Nos. 3,954,474 and 3,982,947 and Jpn. Pat. Appln. KOKOKU Publication No. (hereinafter referred to as JP-B-) 52-28660 can be used. One preferable compound is described in JP-A-63-212932. Antifoggants and stabilizers can be added at any of several different timings, such as before, during, and after grain formation, during washing with water, during dispersion after the washing, before, during, and after chemical sensitization, and before coating, in accordance with the intended application. The antifoggants and the stabilizers can be added during preparation of an emulsion to achieve their original fog preventing effect and stabilizing effect. In addition, the antifoggants and the stabilizers can be used for various purposes of, e.g., controlling crystal habit of grains, decreasing a grain size, decreasing the solubility of grains, controlling chemical sensitization, and controlling an arrangement of dyes.
The photographic emulsion of the present invention is preferably subjected to a spectral sensitization with at least one methine dye or the like, from the viewpoint that the effects desired in the present invention can be exerted. Examples of usable dyes include cyanine dyes, merocyanine dyes, composite cyanine dyes, composite merocyanine dyes, holopolar cyanine dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes. Particularly useful dyes are those belonging to cyanine dyes, merocyanine dyes and composite merocyanine dyes. Any of nuclei commonly used in cyanine dyes as basic heterocyclic nuclei can be applied to these dyes. Examples of such applicable nuclei include a pyrroline nucleus, an oxazoline nucleus, a thiozoline nucleus, a pyrrole nucleus, an oxazole nucleus, a thiazole nucleus, a selenazole nucleus, an imidazole nucleus, a tetrazole nucleus and a pyridine nucleus; nuclei comprising these nuclei fused with alicyclic hydrocarbon rings; and nuclei comprising these nuclei fused with aromatic hydrocarbon rings, such as an indolenine nucleus, a benzindolenine nucleus, an indole nucleus, a benzoxazole nucleus, a naphthoxazole nucleus, a benzothiazole nucleus, a naphthothiazole nucleus, a benzoselenazole nucleus, a benzimidazole nucleus and a quinoline nucleus. These nuclei may have at least one substituent on carbon atoms thereof.
Any of 5 or 6-membered heterocyclic nuclei such as a pyrazolin-5-one nucleus, a thiohydantoin nucleus, a 2-thioxazolidine-2,4-dione nucleus, a thiazolidine-2,4-dione nucleus, a rhodanine nucleus and a thiobarbituric acid nucleus can be applied as a nucleus having a ketomethylene structure to the merocyanine dye or composite merocyanine dye.
These spectral sensitizing dyes may be used either individually or in combination. The spectral sensitizing dyes are often used in combination for the purpose of attaining supersensitization. Representative examples thereof are described in U.S. Pat. Nos. 2,688,545, 2,977,229, 3,397,060, 3,522,052, 3,527,641, 3,617,293, 3,628,964, 3,666,480, 3,672,898, 3,679,428, 3,703,377, 3,769,301, 3,814,609, 3,837,862 and 4,026,707, and GB 1,344,281 and 1,507,803, JP-B""s-43-4936 and 53-12375 and JP-A""s-52-110618 and 52-109925.
The emulsion of the present invention may be doped with a dye which itself exerts no spectral sensitizing effect or a substance which absorbs substantially none of visible radiation and exhibits supersensitization, together with the above spectral sensitizing dye.
The emulsion may be doped with the spectral sensitizing dye at any stage of the process for preparing the emulsion which is known as being useful. Although the doping is most usually conducted at a stage between the completion of the chemical sensitization and before the coating, the spectral sensitizing dye can be added simultaneously with the chemical sensitizer to thereby simultaneously effect the spectral sensitization and the chemical sensitization as described in U.S. Pat. Nos. 3,628,969 and 4,225,666. Alternatively, the spectral sensitization can be conducted prior to the chemical sensitization as described in JP-A-58-113928, and also, the spectral sensitizing dye can be added prior to the completion of silver halide grain precipitation to thereby initiate the spectral sensitization. Further, the above compound can be divided prior to addition, that is, part of the compound can be added prior to the chemical sensitization with the rest of the compound added after the chemical sensitization as taught in U.S. Pat. No. 4,225,666. Still further, the spectral sensitizing dye can be added at any stage during the formation of silver halide grains, such as the method disclosed in U.S. Pat. No. 4,183,756 and other methods.
The addition amount of the spectral sensitizing dye can range from 4xc3x9710xe2x88x926 to 8xc3x9710xe2x88x923 mol per mol of the silver halide. In the case where a preferable silver halide grain size of 0.2 to 1.2 xcexcm, the addition amount of about 5xc3x9710xe2x88x925 to 2xc3x9710xe2x88x923 is effective.
In the lightsensitive material of the present invention, it is only required that at least one silver halide emulsion layer be formed on a support. A typical example is a silver halide photographic lightsensitive material having, on its support, at least one lightsensitive layer constituted by a plurality of silver halide emulsion layers which are sensitive to essentially the same color but have different sensitivities. This lightsensitive layer includes a unit lightsensitive layer which is sensitive to one of blue light, green light and red light. In a multilayered silver halide color photographic lightsensitive material, these unit lightsensitive layers are generally arranged in the order of red-, green- and blue-sensitive layers from a support. However, according to the intended use, this arrangement order may be reversed, or light-sensitive layers sensitive to the same color can sandwich another lightsensitive layer sensitive to a different color.
Various non lightsensitive layers such as an intermediate layer can be formed between the silver halide lightsensitive layers and as the uppermost layer and the lowermost layer. These intermediate layers may contain, e.g., couplers to be described later, DIR compounds and color-mixing inhibitors. As for a plurality of silver halide emulsion layers constituting respective unit lightsensitive layer, a two-layered structure of high- and low-speed emulsion layers can be preferably used in this order so as to the speed becomes lower toward the support as described in DE (German Patent) 1,121,470 or GB 923,045, the disclosures of which are incorporated herein by reference. Also, as described in JP-A""s-57-112751, 62-200350, 62-206541 and 62-206543, the disclosures of which are incorporated herein by reference, layers can be arranged such that a low-speed emulsion layer is formed farther from a support and a high-speed layer is formed closer to the support.
As described in JP-B-49-15495, the disclosure of which is incorporated herein by reference, three layers can be arranged such that a silver halide emulsion layer having the highest sensitivity is arranged as an upper layer, a silver halide emulsion layer having sensitivity lower than that of the upper layer is arranged as an interlayer, and a silver halide emulsion layer having sensitivity lower than that of the interlayer is arranged as a lower layer; i.e., three layers having different sensitivities can be arranged such that the sensitivity is sequentially decreased toward the support. Even when a layer structure is constituted by three layers having different sensitivities, these layers can be arranged in the order of medium-speed emulsion layer/high-speed emulsion layer/low-speed emulsion layer from the farthest side from a support in a layer sensitive to one color as described in JP-A-59-202464, the disclosure of which is incorporated herein by reference. In addition, the order of high-speed emulsion layer/low-speed emulsion layer/medium-speed emulsion layer or low-speed emulsion layer/medium-speed emulsion layer/high-speed emulsion layer can be adopted. Furthermore, the arrangement can be changed as described above even when four or more layers are formed.
Furthermore, in the present invention, the photographic material may also have an emulsion layer having the fourth or more color sensitivity.
The layer of the fourth or more color sensitivity may be a layer that is sensitive to the wavelength region partly different from the region of a blue-sensitive, green-sensitive or red-sensitive layer. The layer of the fourth or more color sensitivity may be sensitive to infrared light or ultraviolet light. Couplers to be used in the layers may be selected depending on the purpose thereof.
The layer structures of the photographic material of the present invention are listed below when the photographic material of the present invention is configured to a three-layer structure. However, the present invention is not limited to these. The order herein is from the layer closest to the support.
1) low-speed red-sensitive emulsion layer (Rlu), medium-speed red-sensitive emulsion layer (RLm), high-speed red-sensitive emulsion layer (Rlo), low-speed green-sensitive emulsion layer (Glu), medium-speed green-sensitive emulsion layer (GLm), high-speed green-sensitive emulsion layer (Glo), low-speed blue-sensitive emulsion layer (Blu), medium-speed blue-sensitive emulsion layer (BLm), and high-speed blue-sensitive emulsion layer (Blo).
2) GLu, GLm, GLo, RLu, RLm, RLo, BLu, BLm, and Blo;
3) GLu, RLu, GLm, RLm, GLo, RLo, BLu, BLm, Blo;
4) GLu, GLm, RLu, RLm, GLo, RLo, BLu, BLm, Blo;
5) RLu, RLm, GLu, GLm, GLo, RLo, BLu, BLm, Blo;
6) GLu, RLu, RLm, GLm, GLo, RLo, BLu, BLm, Blo;
7) RLu, GLu, RLm, GLm, GLo, RLo, BLu, BLm, Blo;
8) GLu, GLm, RLm, Glu, RLo, GLo, BLu, BLm, Blo;
9) RLu, RLm, GLu, GLm, RLo, GLo, BLu, BLm, Blo;
10) GLu, GLm, RLu, RLm, RLo, GLo, BLu, BLm, Blo;
11) RLu, GLu, GLm, RLm, RLo, GLo, BLu, BLm, Blo; and
12) GLu, RLu, GLm, RLm, RLo, GLo, BLu, BLm, Blo
Silver halide photographic lightsensitive material to which the present invention can be applied may contain various additives in accordance with its purposes.
These additives are described in detail in Research Disclosure Item 17643 (December 1978), Item 18716 (November 1979) and Item 308119 (December 1989), the disclosures of which are incorporated herein by reference. A summary of the locations where they are described will be listed in the following table.
With respect to the layer arrangement and related techniques, silver halide emulsions, dye forming couplers, DIR couplers and other functional couplers, various additives and development processing which can be used in the photographic lightsensitive material of the present invention and the emulsions suitable for use in the lightsensitive material, reference can be made to EP 0565096A1 (published on Oct. 13, 1993), the disclosure of which is incorporated herein by reference, and patents cited therein. Individual particulars and the locations where they are described will be listed below.
1. Layer arrangement: page 61 lines 23 to 35, page 61 line 41 to page 62 line 14,
2. Interlayers: page 61 lines 36 to 40,
3. Interlayer effect imparting layers: page 62 lines 15 to 18,
4. Silver halide halogen compositions: page 62 lines 21 to 25,
5. Silver halide grain crystal habits: page 62 lines 26 to 30,
6. Silver halide grain sizes: page 62 lines 31 to 34,
7. Emulsion production methods: page 62 lines 35 to 40,
8. Silver halide grain size distributions: page 62 lines 41 to 42,
9. Tabular grains: page 62 lines 43 to 46,
10. Internal structures of grains: page 62 lines 47 to 53,
11. Latent image forming types of emulsions: page 62 line 54 to page 63 to line 5,
12. Physical ripening and chemical sensitization of emulsion: page 63 lines 6 to 9,
13. Use of Emulsion in mixture: page 63 lines 10 to 13,
14. Fogging emulsions: page 63 lines 14 to 31,
15. Nonlightsensitive emulsions: page 63 lines 32 to 43,
16. Silver coating amounts: page 63 lines 49 to 50,
17. Photographic additives usable in the present invention are also described in RDs. Item 17643 (December, 1978), Item 18716 (November, 1979) and Item 307105 (November, 1979), the disclosures of which are incorporated herein by reference, and the relevant description portions are summarized in the following table.
18. Formaldehyde scavengers: page 64 lines 54 to 57,
19. Mercapto antifoggants: page 65 lines 1 to 2,
20. Fogging agent, etc.-releasing agents: page 65 lines 3 to 7,
21. Dyes: page 65, lines 7 to 10,
22. Color coupler summary: page 65 lines 11 to 13,
23. Yellow, magenta and cyan couplers: page 65 lines 14 to 25,
24. Polymer couplers: page 65 lines 26 to 28,
25. Diffusive dye-forming couplers: page 65 lines 29 to 31,
26. Colored couplers: page 65 lines 32 to 38,
27. Functional coupler summary: page 65 lines 39 to 44,
28. Bleaching accelerator-releasing couplers: page 65 lines 45 to 48,
29. Development accelerator release couplers: page 65 lines 49 to 53,
30. Other DIR couplers: page 65 line 54 to page 66 to line 4,
31. Method of dispersing couplers: page 66 lines 5 to 28,
32. Antiseptic and mildew proofing agents: page 66 lines 29 to 33,
33. Types of sensitive materials: page 66 lines 34 to 36,
34. Thickness of lightsensitive layer and swelling speed: page 66 line 40 to page 67 line 1,
35. Back layers: page 67 lines 3 to 8,
36. Development processing summary: page 67 lines 9 to 11,
37. Developers and developing agents: page 67 lines 12 to 30,
38. Developer additives: page 67 lines 31 to 44,
39. Reversal processing: page 67 lines 45 to 56,
40. Processing solution open ratio: page 67 line 57 to page 68 line 12,
41. Development time: page 68 lines 13 to 15,
42. Bleach-fix, bleaching and fixing: page 68 line 16 to page 69 line 31,
43. Automatic processor: page 69 lines 32 to 40,
44. Washing, rinse and stabilization: page 69 line 41 to page 70 line 18,
45. Processing solution replenishment and recycling: page 70 lines 19 to 23,
46. Developing agent built-in sensitive material: page 70 lines 24 to 33,
47. Development processing temperature: page 70 lines 34 to 38, and
48. Application to film with lens: page 70 lines 39 to 41.